Residual current detection (RCD) and ground monitor interrupter (GMI) are essential functions for safe charging of electric vehicles. The RCD is responsible for interrupting AC power should a conduction path to ground appear in the charging circuit. For example, a person touching live components of an electric vehicle (EV) may cause a conduction path to ground.
The GMI ensures that the ground connection between the EV charger and a utility is continuous and of low impedance. The GMI interrupts AC power to the EV if the ground connection is non-continuous or has high impedance. High impedance or open ground connections may result in dangerous high voltages appearing on the chassis of the EV.
Conventional methods for detecting residual leakage current rely on current transformers, which may be sensitive to AC leakage currents, but can saturate and fail to operate should DC leakage current be present. EV and solar installations may contain dangerously high DC voltages that may cause DC leakage current to be present.